A Dynamic Analysis of Cosmic Strings in the $f(R,T)$ Gravity Model
Abstract
This study investigates the dynamics of cosmic strings within the framework of the $f(R,T)$ gravity model, a modified theory of gravity proposed by Harko et al. in 2011. The $f(R,T)$ theory extends Einstein’s general relativity by including functions of the Ricci scalar ($R$) and the trace of the energy-momentum tensor ($T$). Using the Friedman-Robertson-Walker (FRW) universe model, the study derives the field equations and explores the behavior of the key cosmological parameters, such as the scale factor, string energy density, cosmological term, deceleration parameter, and Hubble parameter. The analytical solutions show that the universe expands continuously with the increasing scale factor values. The study also demonstrates that energy density and the cosmological term decrease over time, while the Hubble parameter exhibits a similar declining trend. The results indicate that the model aligns well with the observed accelerated expansion of the current universe. These findings provide valuable insights into the role of cosmic strings and modified gravity theories in explaining large-scale cosmic evolution.
Keywords
$f(R,T)$ theory, string cloud, FRW space-time, topological defects
Supporting Institution
Çanakkale Onsekiz Mart University
Thanks
This work was supported by the Office of Scientific Research Projects Coordination at Çanakkale Onsekiz Mart University, Grant number: FYL-2020-3267.
References
- A. Vilenkin, E. P. S. Shellard, Cosmic strings and other topological defects, Cambridge University Press, 1994.
- T. W. B. Kibble, Topology of cosmic domains and strings, Journal of Physics A Mathematical General 9 (8) (1976) 1387–1398.
- T. Kanakavalli, G. Ananda Rao, LRS Bianchi type-I string cosmological models in f(R,T) gravity, Astrophysics and Space Science 361 (7) (2016) 206.
- M. Kiran, D. R. K. Reddy, Non-existence of Bianchi type-III bulk viscous string cosmological model in f(R,T) gravity, Astrophysics and Space Science 346 (2) (2013) 521–524.
- A. G. Riess, A. V. Filippenko, P. Challis, A. Clocchiatti, A. Diercks, P. M. Garnavich, R. L. Gilliland, C. J. Hogan, S. Jha, R. P. Kirshner, B. Leibundgut, M. M. Phillips, D. Reiss, B. P. Schmidt, R. A. Schommer, R. C. Smith, J. Spyromilio, C. Stubbs, N. B. Suntzeff, J. Tonry, Observational evidence from Supernovae for an accelerating universe and a cosmological constant, The Astronomical Journal 116 (3) (1998) 1009–1038.
- E. Hubble, A relation between distance and radial velocity among extra-galactic nebulae, Proceedings of the National Academy of Science 15 (3) (1929) 168–173.
- T. Harko, F. S. N. Lobo, S. Nojiri, S. D. Odintsov, f(R,T) gravity, Physical Review D 84 (2) (2011) 024020.
- R. M. Gad, A. Al-Jedani, S. T. Alsulami, Conformal solutions of static plane symmetric cosmological models in cases of a perfect fluid and a cosmic string cloud, Axioms 14 (2) (2025) 117.
- A. Ditta, X. Tiecheng, M. Asia, I. Mahmood, Cloud of strings and quintessence compact stars with anisotropic fluid in symmetric teleparallel gravity, International Journal of Geometric Methods in Modern Physics 21 (4) (2024) 2450076.
- P. M. Lambat, A. M. Pund, Cosmic string coupled with perfect fluid Bianchi type-I universe in f(R,T) modified gravitational theory, in: B. Butey, R. Thete, B. Thakran, A. Deshpande, E. Raut, K. Nandekar, B. Rajvaidya (Eds.), American Institute of Physics Conference Series, Vol. 3139 American Institute of Physics Conference Series, AIP, Nagpur, 2023, 090005.